Does not load dll in mwindows (C ++) mode

I want to load a dll from a hidden process that I compiled with -mwindows in g ++ but it does not load but I remove the flag > -mwindows is loading well.

Here's the code:

  

load_dll.cpp

HINSTANCE hGetProcIDDLL = LoadLibrary("MiLibreria");
f_funci funci = (f_funci)GetProcAddress(hGetProcIDDLL, "funci");
f (!funci) { /*...*/

Dll.cpp

extern "C" __declspec(dllexport) int funci() {
     MessageBoxA(NULL, "HOLA DESDE PLUGIN", "Plugin-msg", NULL);
     return 0;
}

complete compiler line g ++ program.cpp -o calculate.exe -std = c ++ 11 -fno-rtti -fno-inline -O3 -static -static-libstdc ++ -lole32 -loleaut32 -luuid -mwindows